1. Field of Invention
The present invention relates generally to a RF power amplifier (“PA”) integrated circuits (“ICs”), and more particularly, to a power amplifier for use in multi-mode and multi-band wireless communication devices.
2. Discussion of Related Art
Multi-band and Multi-mode power amplifiers have been proposed to address an increasing demand for bandwidth enhancement and flexibility of wireless communication system. To achieve higher data rate, more complicated modulations are adopted, which push wireless system evolution from the second generation (“2G”) to the third generation (“3G”) including three international standards: time division synchronous code division multiple access (“TD-SCDMA”), wide-band code division multiple access/high-speed packet access (“WCDMA/HSPA”), and code division multiple access (“CDMA”) 2000. The frequency bands in 3 G wireless system vary from one area to another. To support global user roaming and global phone design, multi-band RF power amplifiers are required. To support backward compliance with 2G legacy network infrastructure, multi-modes for 3G and 2G need to be supported.
In wireless transmitter system, power amplifiers are often tuned for the frequency and power level of intended operation. In principle, a combination of device size, bias and matching circuits can be optimized for fixed output power, frequency with given process technology. If either frequency or output power is changed, matching network, bias and device size need to be adjusted for optimum performance.
Unfortunately, the adjustability has not been supported by current power amplifier architecture. Various design architecture have been disclosed in the art that expand single band or single mode functionality to multi-band and multi-mode applications. For example, U.S. Pat. No. 5,060,294 to Schwent et al, describes a dual-mode power amplifier. A dual mode power amplifier is an amplifier operating in one of two different modes in a single frequency band. Such an amplifier, however, is not a capable of operating in more than one frequency band.
U.S. Pat. No. 6,970,040 to David Dening describes a wideband power amplifier with multiple inputs and multiple matching circuits that operate to combine the signals in the different frequency bands. In the architecture, each of the matching circuits has to be small impedance in the corresponding one of the plurality of frequency band and large impedance in others of the plurality of frequency bands. However, when frequencies bands are close each other or more than three bands are needed, this architecture will suffers bigger size as well as high loss due to limited quality factor of inductor or capacitors.
Currently, the discrete power amplifier solution is widely used in multi-band and multi mode phones, where parallel multi PA device set are used and one PA device set for a frequency band as shown in FIG. 1. Another solution is used to deal with power level changes as shown in FIG. 2. This solution has good power added efficiency (“PAE”) at one path and worse PAE at another path, which is not tolerable in a lot of multi-bands 3G applications. A multi-modes converged power amplifier is shown in FIG. 3, where multiple paths are used for 3G, Long Term Evolution (“L TE”) and 2G, separately. These three approaches all use parallel have much bigger size and high cost as well as complexity for routing in phone board designs.
It would be highly desirable to have a multi-band and multi mode power amplifier design that can cover wide frequency range and minimizes size and cost. It is therefore an object of the invention to provide a reconfigurable architecture with CMOS Silicon On Insulator (“SOI”) and Gallium Arsenide (“GaAs”) hybrid integration.